F35 fuel tank problems - bubbles cut off fuel delivery to engine?

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1

Posted by williedoylemom (williedoylemom@…>)

We were talking with a F35 owner who said that he has had several
instances of being knocked about by the wakes of power boats and
then having his engine cut off in the middle of a busy boating
channel, the ICW, etc. This is certainly of great concern to us, as
new 35 owners. He supposes that it is becaue the F35 gas tank
(under the aft berth) is wide and not very deep. He feels that its
horizontal nature gives the gas a large surface on which to form
bubbles when sloshed and that these bubbles are then sucked in and
stop the flow of fuel. Sounds like a good explanation. But might it
be something else? If so, what?

Have any other 35 owners had this problem? If so, what did you do
to correct it? We are wondering about a smaller, connected tank
that might be of vertical design and would be fed by the larger,
main tank. The engine would then be fed from mid-tank level in the
small tank, say, and the smaller tank would be always kept fuel so
that bubbles on the top of it would not be sucked into the line.

This, of course, goes against the KISS principle and would,
therefore, but just one more thing to get messed up.

Any thoughts?
Thank you, Faith

2

Posted by lance_ryley (lance_ryley@…>)

Hi Faith,
I can’t speak directly to the F35, but I doubt that it’s bubbles
that would cause this condition. I was warned by the PO of Bright
Star that, in a short choppy sea, that Bright Star might lose power.
His reasoning was that, despite years of keeping the diesel tank
essentially full and treated with biocide, that there was 24 years
worth of culch that had died and settled to the bottom of the tank.
Pounding into a sea would stir up the tank and choke out the filter.
Since the fuel line pulls from the bottom of the tank, this seemed
reasonable, and then it actually happened during the delivery from
Maryland. We spent a horrible, cold, frustrating day coming down the
Delaware river exactly dead into the wind and sea. The Perkins, God
bless her, never faltered until we turned to go into Cape May!
Then, the filtration system failed us. It took me about 45 seconds
to replace the primary filter and restart the engine, but man… it
seemed a lot longer. We had no problems the rest of the trip.

I’d be very surprised if the fuel tank were designed in such a way
that air was so easily sucked into the engine. I’d bet first on
dirty fuel and dirty filters.


Lance

— In freedomyachts2003@yahoogroups.com, “williedoylemom”
<williedoylemom@…> wrote:

We were talking with a F35 owner who said that he has had several
instances of being knocked about by the wakes of power boats and
then having his engine cut off in the middle of a busy boating
channel, the ICW, etc. This is certainly of great concern to us,
as
new 35 owners. He supposes that it is becaue the F35 gas tank
(under the aft berth) is wide and not very deep. He feels that
its
horizontal nature gives the gas a large surface on which to form
bubbles when sloshed and that these bubbles are then sucked in and
stop the flow of fuel. Sounds like a good explanation. But might
it
be something else? If so, what?

Have any other 35 owners had this problem? If so, what did you do
to correct it? We are wondering about a smaller, connected tank
that might be of vertical design and would be fed by the larger,
main tank. The engine would then be fed from mid-tank level in the
small tank, say, and the smaller tank would be always kept fuel
so
that bubbles on the top of it would not be sucked into the line.

This, of course, goes against the KISS principle and would,
therefore, but just one more thing to get messed up.

Any thoughts?
Thank you, Faith

3

Posted by Thomas Wales (twales@…>)

Hi Faith,
I would be inclined to agree with Lance. A few years ago, I “bit
the bullet” and cleaned out the fuel tank on my Dufour 27. It was all
part of the repowering process and I’m very glad I did it. As Lance
indicated, there were years of sediment. I pumped out the diesel fuel and
wiped the interior of the tank clean. I also replace the water seperating
fuel filter. It was a nasty job, but there was a lot of sediment in the
tank. I agree that we should all carry spare filters as part of our
“repair” kit supplies.
Good luck.
TW



At 02:43 PM 2/27/2006 +0000, you wrote:

Hi Faith,
I can’t speak directly to the F35, but I doubt that it’s bubbles
that would cause this condition. I was warned by the PO of Bright
Star that, in a short choppy sea, that Bright Star might lose power.
His reasoning was that, despite years of keeping the diesel tank
essentially full and treated with biocide, that there was 24 years
worth of culch that had died and settled to the bottom of the tank.
Pounding into a sea would stir up the tank and choke out the filter.
Since the fuel line pulls from the bottom of the tank, this seemed
reasonable, and then it actually happened during the delivery from
Maryland. We spent a horrible, cold, frustrating day coming down the
Delaware river exactly dead into the wind and sea. The Perkins, God
bless her, never faltered until we turned to go into Cape May!
Then, the filtration system failed us. It took me about 45 seconds
to replace the primary filter and restart the engine, but man… it
seemed a lot longer. We had no problems the rest of the trip.

I’d be very surprised if the fuel tank were designed in such a way
that air was so easily sucked into the engine. I’d bet first on
dirty fuel and dirty filters.

Lance

— In freedomyachts2003@yahoogroups.com, “williedoylemom”
<williedoylemom@…> wrote:

We were talking with a F35 owner who said that he has had several
instances of being knocked about by the wakes of power boats and
then having his engine cut off in the middle of a busy boating
channel, the ICW, etc. This is certainly of great concern to us,
as
new 35 owners. He supposes that it is becaue the F35 gas tank
(under the aft berth) is wide and not very deep. He feels that
its
horizontal nature gives the gas a large surface on which to form
bubbles when sloshed and that these bubbles are then sucked in and
stop the flow of fuel. Sounds like a good explanation. But might
it
be something else? If so, what?

Have any other 35 owners had this problem? If so, what did you do
to correct it? We are wondering about a smaller, connected tank
that might be of vertical design and would be fed by the larger,
main tank. The engine would then be fed from mid-tank level in the
small tank, say, and the smaller tank would be always kept fuel
so
that bubbles on the top of it would not be sucked into the line.

This, of course, goes against the KISS principle and would,
therefore, but just one more thing to get messed up.

Any thoughts?
Thank you, Faith

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4

Posted by sodaksparrowhawk (sodaksparrowhawk@…>)

Happened twice, once each on hull no. 25 and hull no. 57. Both times
with about seven gallons fuel remaining(or slightly less).

Both times my first thought was contamination, both times filters were
clean.

Did not think “bubbles” or frothing were the cause, but rather that
the fuel pickup was momentarily not submerged as the fuel remaining
ran to the “downhill” side and “she sucked a gulp of air”.

Hope this explains.

Stan

5

Posted by macks011 (macks04@…>)

This is a problem that sometimes appears with shallow off center
tanks. It happened with my 36 and I solved it with an added fuel
pump, filters and manifold. If you are interested, I have text and
photos available.


— In freedomyachts2003@yahoogroups.com, “williedoylemom”
<williedoylemom@…> wrote:

We were talking with a F35 owner who said that he has had several
instances of being knocked about by the wakes of power boats and
then having his engine cut off in the middle of a busy boating
channel, the ICW, etc. This is certainly of great concern to us,
as
new 35 owners. He supposes that it is becaue the F35 gas tank
(under the aft berth) is wide and not very deep. He feels that
its
horizontal nature gives the gas a large surface on which to form
bubbles when sloshed and that these bubbles are then sucked in and
stop the flow of fuel. Sounds like a good explanation. But might
it
be something else? If so, what?

Have any other 35 owners had this problem? If so, what did you do
to correct it? We are wondering about a smaller, connected tank
that might be of vertical design and would be fed by the larger,
main tank. The engine would then be fed from mid-tank level in the
small tank, say, and the smaller tank would be always kept fuel
so
that bubbles on the top of it would not be sucked into the line.

This, of course, goes against the KISS principle and would,
therefore, but just one more thing to get messed up.

Any thoughts?
Thank you, Faith

6

Posted by Skip Turpin (skipperf33@…>)

I have not given this a great deal of thought so it may be just a
hair-brained idea! In this case the advice is worth about what you
paid for it.

If the problem is air being sucked into the fuel system wether it be
from foam or just a momentarily exposed fuel pickup. Why not mount a
good sized water separator with a see through bulb only mount it
upside down. That way when the fuel/air mixture gets to this
separator the air would naturally rise to the top of the bulb where
it would be easily seen and removed in about two seconds with no loss
of clear fuel to the engine.

I see a number of challenges with this type of fix!

  1. You would want the separator mounted in a very accessible
    location for fast ID and removal of the air. This could be just
    about anywhere that you feel would be convenient to observe and use.

  2. If you want to mount the separator high in the system, you
    would need to install an auxiliary electric fuel pump to pressurize
    the system, otherwise when you opened the valve to let the air out,
    you would actually pull more air in due to gravity.

  3. If you want to forgo the use of an auxiliary fuel pump, you
    would have to mount the separator in a position that would allow for
    gravity feed to it. Depending on the location of your tank, this
    might leave your separator in a very undesirable or inaccessible
    location.

I know there are special valves that separate air from liquid, but I
don’t think I would be willing to trust any of them. If they were to
stick open. . . well I think you get the picture, and the smell, and
the mess. Yikes!

Another advantage to having an electric fuel pump with this system
would be the ease with which you could pump all the usable (or
contaminated) fuel out your tank in order to do some serious chemical
tank cleaning. This system could allow you to re-circulate the
chemical and the small amount of residual fuel through say a 2 or 3
micron filter to polish it. I did this on my F33 using a hand held
electric pump, some Jerry cans and a “Frantz” oil filter, worked
great! After three trips though the Frantz all my fuel was
sparkling clean and no mess or BILL to pay!

As I prefaced this, I have not given this idea a lot of thought, so
if someone wants to shoot holes in it, have at it!

Skip

7

Posted by Jay T. Reed (reedjayt@…>)

Faith

We’ve had our 1994 Freedom 35 for 2 years. We’ve had it out in all types of
conditions, including runing up the Delaware, on our way to the Chesapeake
from Newport RI, under power in rollarcoaster type waves and never had a
problem. I change both fuel filters every year, at the end of the season
and I haven’t let the tank get below about 10 gal.

Jay

From: “williedoylemom” <williedoylemom@…>
Reply-To: freedomyachts2003@yahoogroups.com
To: freedomyachts2003@yahoogroups.com
Subject: [freedomyachts2003] F35 fuel tank problems - bubbles cut off fuel
delivery to engine?
Date: Mon, 27 Feb 2006 13:56:08 -0000

We were talking with a F35 owner who said that he has had several
instances of being knocked about by the wakes of power boats and
then having his engine cut off in the middle of a busy boating
channel, the ICW, etc. This is certainly of great concern to us, as
new 35 owners. He supposes that it is becaue the F35 gas tank
(under the aft berth) is wide and not very deep. He feels that its
horizontal nature gives the gas a large surface on which to form
bubbles when sloshed and that these bubbles are then sucked in and
stop the flow of fuel. Sounds like a good explanation. But might it
be something else? If so, what?

Have any other 35 owners had this problem? If so, what did you do
to correct it? We are wondering about a smaller, connected tank
that might be of vertical design and would be fed by the larger,
main tank. The engine would then be fed from mid-tank level in the
small tank, say, and the smaller tank would be always kept fuel so
that bubbles on the top of it would not be sucked into the line.

This, of course, goes against the KISS principle and would,
therefore, but just one more thing to get messed up.

Any thoughts?
Thank you, Faith